The principal aim of this research is to extend our understanding of the acute effects of graded doses of three central nervous system depressants on human cognitive functioning. The drugs studied in the original proposal were secobarbital sodium, methaqualone HC1, and meprobamate. Since the highest dose of meprobamate (20.5 mg/kg) produced little effect in sensitive information processing tasks, we propose to discontinue the study of that drug and substitute ethyl alcohol. Each of the drugs will be tested in six multiple factor experiments. The several experiments are designed to converge on the question of the locus (or loci) of drug effects on specific theoretical operations (stages) in current models of information processing and memory. Our present data suggest that secobarbital and methaqualone slow very early processes on the stimulus input side, whereas alcohol disrupts operations on the output side (e.g., response selection and organization). All three drugs seem to impair memorial processes related both to short-term store and long-term store. The proposed experiments should provide a finer-grained analysis of the drug's effects while providing some integration of the previous findings from information processing and memorial tasks. The range of proposed doses is sufficiently wide to separate drug effects from dose effects.